Refrigerated merchandiser with modular evaporator coils and EEPR control

Abstract

An air cooling and control system for a refrigerated food merchandiser having an insulated cabinet with a product area having adjacent product zones, plural modular evaporator coil sections of substantially equal heat exchange potential and being of predetermined length and arranged in horizontal, spaced, end-to-end predetermined disposition and separate air moving means associated with each coil section and a corresponding product zone for circulating separate air flows through the coil sections and to the product area for cooling. The system further includes a first refrigerant metering valve for controlling liquid refrigerant flow on the high side of the evaporator sections, and a second refrigerant metering valve for controlling suction pressure and refrigerant vapor flow on the low side of the evaporator sections. An electronic control senses exit air temperatures downstream of the evaporator sections and operates the second metering valve in response thereto. In another aspect, a method of operating an electronic evaporator pressure regulating (EEPR) valve during the refrigeration and defrost modes of the controlled evaporator and in response to sensed air temperatures .

What is claimed is:  
     
       1. An air cooling system in a commercial refrigerated merchandiser having an insulated cabinet with a product area having a least two horizontally adjacent side-by-side product zones for the display and marketing of food products, said system comprising: 
       modular evaporator means having at least two separate coil sections of preselected length and heat exchange capability, said coil sections being horizontally disposed with their adjacent ends in spaced apart, end-to-end orientation relative to each other in said cabinet;  
       liquid refrigerant metering means for controlling the inlet flow of liquid refrigerant on the high side of said modular evaporator means;  
       said plural coil sections of said modular evaporator means being constructed and arranged in parallel refrigerant flow relationship with each other to receive liquid refrigerant from said liquid refrigerant metering means, and all of said coil sections having an operative cooling mode at the same time and an inoperative defrost mode at the same time; and  
       separate air moving means associated with the respective coil sections for circulating separate air flows through said coil sections and being constructed and arranged with air flow passageways in said cabinet for discharging the air flows in side-by-side relationship to the horizontally adjacent side-by-side product zones for cooling.  
     
     
       2. The air cooling system of  claim 1  which includes other refrigerant metering means constructed and arranged on the low side of said modular evaporator means for controlling the suction pressure in at least one coil section thereof. 
     
     
       3. The air cooling system of  claim 2  which includes means for periodically defrosting said evaporator means, and in which said other refrigerant metering means includes means for sensing air temperature and adjusting the suction pressure during defrost. 
     
     
       4. The air cooling system of  claim 2 , in which said other metering means includes electronic evaporator pressure regulating (EEPR) valve means for modulating the refrigerant vapor flow rate from the coil sections of said evaporator means, and means for sensing the exit air temperature downstream of said at least one coil section, and controller means for operating said EEPR valve means in a refrigeration mode and in a defrost mode. 
     
     
       5. The air cooling system of  claim 4 , in which said liquid and other metering means and said EEPR valve means are all located within the merchandiser cabinet. 
     
     
       6. The air cooling system of  claim 4 , in which said controller means is constructed and arranged for closing said EEPR valve means during an initial de-icing period of the defrost mode, and is also arranged for modulating the EEPR valve means in an open position during a drip time period of the defrost mode in response to sensed exit air temperatures exceeding a preset value whereby to provide a refrigerating condition at the preset value for the remaining drip time of the defrost mode. 
     
     
       7. An air cooling system in a commercial refrigerated merchandiser having an insulated cabinet with a product area having horizontally adjacent product zones for the display and marketing of food products, said system comprising: 
       modular evaporator means having a plurality of separate coil sections of substantially equal size and heat exchange capability, said plural coil sections having a preselected length and being horizontally disposed in spaced apart, end-to-end orientation relative to each other in said cabinet;  
       liquid refrigerant metering means for controlling the inlet flow of liquid refrigerant on the high side of said modular evaporator means;  
       said plural coil sections of said modular evaporator means being constructed and arranged in parallel refrigerant flow relationship with each other and in series flow relationship with said liquid refrigerant metering means, and all of said coil sections having an operative cooling mode at the same time and an inoperative defrost mode at the same time; and  
       separate air moving means associated with the respective coil sections for circulating separate air flows through said coil sections and discharging the air flows to the adjacent product zones for cooling.  
     
     
       8. The air cooling system of  claim 7 , in which said merchandiser is constructed and arranged with means for normally closing the product area from ambient during the cooling mode, and said liquid refrigerant metering means comprising a single thermostatic expansion valve , and piping means of substantially equal length connecting the outflow side of said expansion valve to each of said coil sections. 
     
     
       9. The air cooling system of  claim 7 , in which said merchandiser is constructed and arranged with the front side of said product area being open to ambient at all times, and said liquid refrigerant metering means comprising at least two thermostatic expansion valves operatively connected on the outflow side to at least two corresponding and separate coil sections. 
     
     
       10. The air cooling system of  claim 7  which includes other refrigerant metering means constructed and arranged on the low side of said modular evaporator means for controlling the suction pressure in at least one coil section thereof. 
     
     
       11. The air cooling system of  claim 10  which includes the means for periodically defrosting all of said evaporator means, and in which said other refrigerant metering means includes means for sensing exit air temperature and adjusting the suction pressure during defrost. 
     
     
       12. The air cooling system of  claim 10 , in which said other metering means includes evaporator pressure regulating (EEPR) valve means for modulating the refrigerant vapor flow rate from the coil sections of said modular evaporator means, and means for sensing the exit air temperature downstream of said at least one coil section, and controller means for operating said EER valve means in a refrigeration mode and in a defrost mode. 
     
     
       13. The air cooling system of  claim 12 , in which said liquid and other metering means and said EEPR valve means are all located within the merchandiser cabinet. 
     
     
       14. The air cooling system of  claim 12 , in which said controller means is constructed and arranged for closing said EEPR valve means during an initial de-icing period of the defrost mode, and is also arranged for modulating the EEPR valve means in an open position during a drip time period of the defrost mode in response to sensed exit air temperatures exceeding a preset value whereby to provide a refrigerating condition at the preset value for the remaining drip time of the defrost mode. 
     
     
       15. An air cooling system in a commercial refrigerated merchandiser having an insulated cabinet with a product zone, comprising: 
       evaporator means having a refrigeration mode and being constructed and arranged for cooling air within the cabinet to achieve a preselected exit air temperature down stream thereof, liquid refrigerant metering means for controlling the flow of liquid refrigerant to the high side of said evaporator means, for circulating air flow through said evaporator means and said product zone; and  
       other refrigerant metering means constructed and arranged on the low side of said evaporator means for controlling the suction pressure thereof, said other metering means comprising evaporator pressure regulating (EEPR) valve means for modulating the refrigerant vapor flow from said evaporator means, and means for sensing exit air temperatures downstream of said evaporator means, and controller means responsive to said sensing means for operating said EEPR valve means in the refrigeration mode and in a defrost mode.  
     
     
       16. The air cooling system of  claim 15 , in which said controller means is constructed and arranged for closing said EEPR valve means during an initial de-icing period of the defrost mode, and is also arranged for modulating the EEPR valve means in an open position during a drip time period of the defrost mode in response to sensed exit air temperatures exceeding a preset value whereby to provide a refrigerating condition at the preset value for the remaining drip time of the defrost mode. 
     
     
       17. The method of controlling the exit air temperature from the evaporator coil in a commercial refrigerated merchandiser for food products, in which the evaporator coil has a refrigeration mode and a defrost mode and the suction side of the evaporator coil has an electronic evaporator pressure regulator (EEPR) valve operated by a valve controller circuit, said control method comprising the steps of: 
       (a) sensing the exit air temperature from the evaporator coil and generating a signal corresponding thereto;  
       (b) operating the EEPR valve in the refrigeration mode of the evaporator coil by modulating refrigerant vapor flow therethrough to maintain a preselected exit air temperature;  
       (c) operating the EEPR valve in the defrost mode of the evaporator coil,  
       (1) by first closing the EEPR valve during a preselected de-icing period of said evaporator coil until reaching a predetermined drip temperature, and  
       (2) then activating the valve controller circuit in response to detection of exit air temperatures exceeding a preselected value during a final drip period to provide limited refrigeration to maintain the preselected temperature during the remainder of the defrost mode.  
     
     
       18. A control method as set forth in  claim 17  wherein the step of operating the EEPR valve in the refrigeration mode further comprises the steps of: 
       (1) monitoring the position of the EEPR valve,  
       (2) timing a preselected period following the onset of operation of the EEPR valve in the refrigeration mode, the time period being selected to permit the valve to substantially stabilize in a position which maintains the exit air temperature at a set point,  
       (3) saving a reference position of the valve at a time when the preselected period is timed out.  
     
     
       19. A control method as set forth in  claim 18  in which the evaporator has a pull down mode, the control method further comprising the steps of: 
       (d) operating the EEPR valve in the pull down mode of the evaporator coil,  
       (1) by first moving the EEPR valve to its full open position,  
       (2) holding the EEPR valve in its full open position until the preselected exit air temperature is detected.  
     
     
       20. A control method as set forth in  claim 19  wherein the step of operating the EEPR valve in the pull down mode further comprises the step, following detection of the preselected exit air temperature, of: 
       (3) setting the EEPR valve at the valve reference position stored in the valve controller during operation of the EEPR valve in the refrigeration mode.  
     
     
       21. A control method as set forth in  claim 17  in which the evaporator has a pull down mode, the control method further comprising the steps of: 
       (d) operating the EEPR valve in the pull down mode of the evaporator coil,  
       (1) by first moving the EEPR valve to its full open position,  
       (2) holding the EEPR valve in its full open position until the preselected exit air temperature is detected.  
     
     
       22. An air cooling system for a commercial refrigerated merchandiser having an insulated cabinet with a product area having at least two horizontally adjacent product zones for the display and marketing of food products, said system comprising: 
       modular evaporator means having at least two separate coil sections of predetermined size and heat exchange capability, said coil sections being horizontally disposed with their adjacent ends in spaced apart orientation with each other and each coil section being operatively associated with one of the product zones for the refrigeration thereof;  
       first refrigerant metering means for controlling the inlet flow of liquid refrigerant to the high side of said modular evaporator means;  
       said plural coil sections of said modular evaporator means being constructed and arranged in parallel refrigerant flow relationship with each other to receive liquid refrigerant from said liquid refrigerant metering means, and all of said coil sections having an operative cooling mode at the same time and an inoperative defrost mode at the same time; and  
       separate air moving means associated with the respective coil sections for circulating separate air flows through said coil sections and being constructed and arranged with separate air flow passageways in said cabinet for discharging the air flows to the horizontally adjacent product zones for cooling.  
     
     
       23. The air cooling system of  claim 22 , in which said cabinet is constructed and arranged with means for normally closing the product area from ambient during the cooling mode, and said first refrigerant metering means comprising a single thermostatic expansion valve, and piping means of substantially equal length connecting the outflow side of said expansion valve to each of said modular coil sections. 
     
     
       24. The air cooling system of  claim 22 , in which said cabinet is constructed and arranged with the front side of said product area being open to ambient at all times, and said first refrigerant metering means comprising at least two thermostatic expansion valves operatively connected on the outflow side to at least two corresponding and separate modular coil sections. 
     
     
       25. The air cooling system of  claim 22  which includes other refrigerant metering means constructed and arranged on the low side of said modular evaporator means for controlling the suction pressure in at least one coil section thereof. 
     
     
       26. The air cooling system of  claim 25  which includes means for periodically defrosting said evaporator means, and in which said second refrigerant metering means includes means for sensing exit air temperature from at least one coil section and adjusting the suction pressure thereof during defrost. 
     
     
       27. The air cooling system of  claim 25 , in which said second refrigerant metering means includes electronic evaporator pressure regulating (EEPR) valve means for modulating the refrigerant vapor flow rate from at least one coil section of said evaporator means, and means for sensing the exit air temperature downstream of said one coil section, and controller means for operating said EEPR valve means in a refrigeration mode and in a defrost mode. 
     
     
       28. The air cooling system of  claim 27 , in which said controller means is constructed and arranged for closing said EEPR valve means during an initial de-icing period of the defrost mode, and is also arranged for modulating the EEPR valve means in an open position during a drip time period of the defrost mode in response to sensed exit air temperatures exceeding a preset value whereby to provide a refrigerating condition at the preset value for the remaining drip time of the defrost mode. 
     
     
       29. The air cooling system of  claim 22 , in which the length of a first of the horizontally adjacent product zones extends angularly relative to the length of a second of the horizontally adjacent product zones, and in which the coil sections associated with said first and second of the horizontally adjacent product zones are non-collinearly disposed in said cabinet. 
     
     
       30. The air cooling system of  claim 22 , in which said product area includes a third product zone horizontally adjacent to and contiguous with said first of the horizontally adjacent product zones, and in which the coil sections associated with said first and third horizontally adjacent product zones are collinearly disposed in end-to-end relationship in said cabinet. 
     
     
       31. In combination with a commercial refrigerated merchandiser having an insulated cabinet with a product area having at least two horizontally adjacent product zones of predetermined length for the display and marketing of food products, a refrigeration system comprising: 
       modular air cooling and circulating means having at least two separate evaporator coil sections of predetermined heat exchange capability, each coil section having elongated coil tubing of preselected length corresponding substantially to the length of an associated one of said product zones, and further having separate air moving means for the circulation of refrigerating air flow across each of the respective coil sections;  
       liquid refrigerant metering means for controlling the inlet flow of liquid refrigerant to the high side of said coil sections;  
       said coil sections of said modular air cooling means being constructed and arranged in parallel refrigerant flow relationship with each other to receive liquid refrigerant from said liquid refrigerant metering means, and all of said coil sections having an operative cooling mode at the same time and an inoperative defrost mode at the same time; and  
       said modular air cooling and circulating means being constructed and arranged in said insulated cabinet with each coil section and its air moving means being in operative relationship with its associated product zone for the circulation of separate air flows through the coil sections and the discharge of such air flows separately to the adjacent product zones for cooling.  
     
     
       32. The refrigerated merchandiser of  claim 31  in which the refrigeration system includes other refrigerant metering means constructed and arranged on the low side of said coil sections for controlling the suction pressure in at least one coil section thereof. 
     
     
       33. The refrigerated merchandiser of  claim 32 , in which said other metering means includes electronic evaporator pressure regulating (EEPR) valve means for modulating the refrigerant vapor flow rate from the modular coil sections, and means for sensing the exit air temperature downstream of said at least one coil section, and controller means for operating said EEPR valve means in a refrigeration mode and in a defrost mode. 
     
     
       34. The refrigerated merchandiser of  claim 33 , in which said controller means is constructed and arranged for closing said EEPR valve during an initial de-icing period of the defrost mode, and is also arranged for modulating the EEPR valve means in an open position during a drip time period of the defrost mode in response to sensed exit air temperatures exceeding a preset value whereby to provide a refrigerating condition at the preset value for the remaining drip time of the defrost mode. 
     
     
       35. The refrigerated merchandiser of  claim 31 , in which said cabinet is constructed and arranged with means for normally closing the product area from ambient during the cooling mode, and said liquid refrigerant metering means comprising a single thermostatic expansion valve, and piping means of substantially equal length connecting the outflow side of said expansion valve to each of said coil sections. 
     
     
       36. The refrigerated merchandiser of  claim 31 , in which said cabinet is constructed and arranged with the front side of said product area being open to ambient at all times, and said liquid refrigerant metering means comprising at least two thermostatic expansion valves operatively connected on the outflow side to at least two corresponding and separate coil sections. 
     
     
       37. The refrigerated merchandiser of  claim 31 , in which the length of a first of the horizontally adjacent product zones extends angularly relative to the length of a second of the horizontally adjacent product zones, and in which the coil sections associated with said first and second of the horizontally adjacent product zones are non-collinearly disposed in said cabinet. 
     
     
       38. The refrigerated merchandiser of  claim 37 , in which said product area includes a third product zone horizontally adjacent to and contiguous with said first of the horizontally adjacent product zones, and in which the coil sections associated with said first and third horizontally adjacent product zones are collinearly disposed in end-to-end relationship in said cabinet. 
     
     
       39. An air cooling system in a commercial refrigerated merchandiser having an insulated cabinet with a product zone, comprising: 
       
         evaporator means having a refrigeration mode and being constructed and arranged for cooling air within the cabinet to achieve a preselected exit air temperature downstream thereof, liquid refrigerant metering means for controlling the flow of liquid refrigerant to the high side of said evaporator means, means for circulating air flow through said evaporator means and said product zone; and  
       
         other refrigerant metering means constructed and arranged on the low side of said evaporator means for controlling the suction pressure thereof, said other metering means comprising evaporator pressure regulating  ( EEPR )  valve means for modulating the refrigerant vapor flow from said evaporator means, said EEPR valve means including an EEPR valve and a stepper motor for actuating said EEPR valve to modulate the low side refrigerant vapor flow, means for sensing exit air temperatures downstream of said evaporator means, and controller means responsive to said sensing means for operating the stepper motor to actuate said EEPR valve in the refrigeration mode and in a defrost mode of the air cooling system.   
     
     
       40. The air cooling system of  claim 39  in which said controller means is constructed and arranged to monitor the position of the EEPR valve in the refrigeration mode for a preselected period of time following the onset of the refrigeration mode and to store a reference position of the valve at the end of the preselected period. 
     
     
       41. The air cooling system of  claim 40  in which said controller means is constructed and arranged to operate the stepper motor to move the EEPR valve to said reference position following the defrost mode. 
     
     
       42. The air cooling system of  claim 39  in which the stepper motor moves the EEPR valve through a predetermined number of incremental steps to a new position for affecting the exit air temperature in response to said means for sensing exit air temperature upon receiving a signal from said controller means, said controller means being constructed and arranged to control the stepper motor for moving the EEPR valve in the refrigeration mode so that the EEPR valve always approaches the new position from the same direction. 
     
     
       43. The air cooling system of  claim 42  wherein said controller means controls the stepper motor to move the EEPR valve to the new position during the refrigeration mode only in a direction which causes the valve to be more open. 
     
     
       44. The air cooling system of  claim 39  in which said liquid refrigerant means comprises an expansion valve and means for sensing temperature of the refrigerant on the low side of said evaporator means, the expansion valve being responsive to said means for sensing refrigerant temperature to modulate the flow of liquid refrigerant into said evaporator means to maintain a substantially constant superheat temperature. 
     
     
       45. A method of controlling the exit air temperature from the evaporator coil in a commercial refrigerated merchandiser for food products, in which the evaporator coil has a refrigeration mode and a defrost mode, said control method comprising the steps of: 
       ( a )  providing an electronic evaporator pressure regulator  ( EEPR )  valve actuated by a stepper motor operated by a valve controller circuit,    
       ( b )  sensing the exit air temperature from the evaporator coil and generating a signal corresponding thereto;    
       ( c )  operating the stepper motor in response to said signal to move the EEPR valve during the refrigeration mode of the evaporator coil for modulating refrigerant vapor flow therethrough to maintain a preselected exit air temperature    
       ( d )  operating the stepper motor to a predetermined position of the EEPR valve in the defrost mode.   
     
     
       46. The method of  claim 45  further comprising: 
       ( a )  monitoring the position of the EEPR valve during the refrigeration mode,    
       ( b )  timing a preselected period following the onset of operation of the EEPR valve in the refrigeration mode, the time period being selected to permit the valve to substantially stabilize in a position which maintains the exit air temperature at a set point,    
       ( c )  storing a reference position of the EEPR valve at the end of the preselected period.   
     
     
       47. The method of  claim 46  further comprising the step of operating the stepper motor to move the EEPR valve to the stored reference position at the onset of operation in the refrigeration mode following the defrost mode. 
     
     
       48. The method of  claim 45  in which the step of operating the stepper motor comprises the step of activating the stepper motor for movement through a selected number of incremental steps corresponding to the signal. 
     
     
       49. The method of  claim 45  in which operating the stepper motor to move the EEPR valve includes moving the valve to a new position, said step of moving comprising always approaching the new position from the same direction during the refrigeration mode. 
     
     
       50. The method of  claim 49  in which moving the valve to a new position during the refrigeration mode comprises always moving the EEPR valve means to the new position in a direction which causes the valve to be more open. 
     
     
       51. The method of  claim 45  further including the step of controlling the flow of liquid refrigerant to the high side of the evaporator coil to maintain a substantially constant superheat temperature on the low side of the evaporator coil. 
     
     
       52. A method of controlling the flow of liquid refrigerant through an evaporator coil in a commercial refrigerated merchandiser for food products, in which the evaporator coil has a refrigeration mode and a defrost mode and a low side of the evaporator coil has an electronic evaporator pressure regulator (EEPR) valve operated by a valve controller circuit, said control method comprising the steps of: 
       ( a )  maintaining exit air temperature in the refrigeration mode at a set point by modulating the EEPR valve in response to sensed exit air temperature from the evaporator coil,    
       ( b )  monitoring the position of the EEPR valve,    
       ( c )  timing a preselected period following the onset of operation of the EEPR valve in the refrigeration mode, the time period being selected to permit the valve to substantially stabilize in a position which maintains the exit air temperature at the set point,    
       ( d )  storing a reference position of the EEPR valve at the end of the preselected period,    
       ( e )  entering the defrost mode by closing the EEPR valve,    
       ( f )  setting the EEPR valve at the stored reference position at the conclusion of the defrost mode upon entry into the refrigeration mode.   
     
     
       53. An air cooling system in a commercial refrigerated merchandiser having an insulated cabinet with a product zone, comprising: 
       
         evaporator means having a refrigeration mode and being constructed and arranged for cooling air within the cabinet to achieve a preselected exit air temperature downstream thereof, liquid refrigerant metering means for controlling the flow of liquid refrigerant to the high side of said evaporator means, means for circulating air flow through said evaporator means and said product zone; and  
       
         other refrigerant metering means constructed and arranged on the low side of said evaporator means for controlling the suction pressure thereof, said other metering means comprising evaporator pressure regulating  ( EEPR )  valve means for modulating the refrigerant vapor flow from said evaporator means, said EEPR valve means including an EEPR valve and a stepper motor for actuating said EEPR valve to modulate the low side refrigerant vapor flow including means for sensing exit air temperatures downstream of said evaporator means, and controller means responsive to said sensing means for operating the stepper motor to actuate said EEPR valve in the refrigeration mode and in a defrost mode of the air cooling system, the stepper motor being constructed and arranged to move the EEPR valve through a predetermined number of incremental steps to a new position for affecting the exit air temperature in response to said means for sensing exit air temperature upon receiving a signal from said controller means, said controller means being constructed and arranged to control the stepper motor for moving the EEPR valve in the refrigeration mode so that the EEPR valve always approaches the new position from the same direction.   
     
     
       54. The air cooling system of  claim 53  wherein said controller means controls the stepper motor to move the EEPR valve to the new position during the refrigeration mode only in a direction which causes the valve to be more open. 
     
     
       55. The air cooling system of  claim 15  in which said EEPR valve means includes an EEPR valve and a stepper motor for actuating said EEPR valve to modulate low side refrigerant vapor flow in the refrigeration mode and for moving the EEPR valve to a predetermined position in the defrost mode. 
     
     
       56. The air cooling system of  claim 55  in which said controller means is constructed and arranged to monitor the position of the EEPR valve in the refrigeration mode for a preselected period of time following the onset of the refrigeration mode and to store a reference position of the valve at the end of the preselected period. 
     
     
       57. The air cooling system of  claim 56  in which said controller means is constructed and arranged to operate the stepper motor to move the EEPR valve to said reference position following the defrost mode. 
     
     
       58. The air cooling system of  claim 55  in which the stepper motor moves the EEPR valve through a predetermined number of incremental steps to a new position for affecting the exit air temperature in response to said means for sensing exit air temperature upon receiving a signal from said controller means, said controller means being constructed and arranged to control the stepper motor for moving the EEPR valve in the refrigeration mode so that the EEPR valve always approaches the new position from the same direction. 
     
     
       59. The air cooling system of  claim 58  wherein said controller means controls the stepper motor to move the EEPR valve to the new position during the refrigeration mode only in a direction which causes the valve to be more open.